IgE Cross-reactivity with Caseins from Different Species in Humans Allergic to Cow's Milk

Fifty-eight sera from humans allergic to cow's milk proteins were analysed for the specificity of their IgE response to the whole casein fraction of milk from different ruminant and nonruminant species (e.g. cow, sheep, goat, rabbit and rat). IgE-specific responses were determined by an enzyme allergosorbent test using the purified casein fractions as immobilized antigen and an anti-human IgE monoclonal antibody labelled with acetylcholinesterase. Co-and/or cross-sensitizations to caseins of the different ruminant species occurred extensively, though IgE responses to ovine and caprine casein appeared to be lower than that obtained with bovine casein. Cross-reactivity is suggested by the significant reactivity of rat and rabbit casein toward human IgE. In terms of specificity and intensity, the IgE response to caseins demonstrates a great variability. Structural homologies in caseins of such different species, that can share common epitopes for the IgE of some patients, suggest that prevention of cow's milk allergy cannot be achieved by using milk from other species as substitutes.